Voltammetry of microparticles used to date archeological artifacts made of copper and bronze
How can the age of archeological objects be determined if the well-established carbon dating method does not apply, for example for metal objects? Spanish and Portuguese scientists have now introduced a technique for dating artifacts made of copper and bronze. Presented in the journal Angewandte Chemie, their electroanalytical method is based on the voltammetry of microparticles. It compares various corrosion products that form over long periods of time and works with only a few nanograms of material so it causes almost no damage.
Voltammetric experiments produce current–voltage curves that have characteristic shapes for many compounds. In order to date copper-containing, archaeological finds, a team led by Antonio Doménech-Carbó at the University of Valencia examined the ratios of two different copper oxides, tenorite and cuprite, that can be differentiated and quantified based on their voltammetric curves.
When they are exposed to air, copper surfaces become covered by a natural layer of cuprite (Cu2O). Over time, this layer is slowly converted to other products of corrosion. As copper-containing objects age in a slightly corrosive environment, without contact with soils or sea air, a layer of tenorite (CuO) continuously forms over the primary cuprite patina. This occurs because cuprite reacts with oxygen from the air to preferentially form tenorite in an atmosphere containing CO2 or in the presence of calcareous materials. Examination of copper coins by scanning electron microscopy coupled with X-ray spectroscopy confirmed the presence of cuprite and tenorite.
To carry out the electroanalytical experiments, the researchers impregnate a graphite bar electrode with paraffin and dab the surface of the artifact with it. A few nanograms of the sample surface stick to the electrode, which is then dipped into an aqueous electrolyte. This causes almost no damage to the object. Copper oxide microparticles result in very characteristic peaks in the resulting current–voltage curves.
Of particular interest to the researchers is the ratio of the current peaks for tenorite and cuprite. It shows a steady increase with increasing corrosion time, as demonstrated with a series of antique coins from various collections, including the Prehistory Museums of València and Xàtiva (Spain), as well as the artificial ageing of Euro cent coins made of copper. The researchers were able to use the coins to establish a calibration curve that can be used to date objects of unknown age.
The voltammetric dating of a water pitcher from the Caliphal period and a Montefortino helmet from the Roman age gave ages of 1050±80 and 2150±150 years, respectively, which agree well with dates previously established from the archaeological context.
About the Author
Dr. Antonio Doménech-Carbó is Professor at the Department of Analytical Chemistry of the University of Valencia, Spain. His research field is electrochemistry, in particular focused on electroanalytical methods for archaeometry, conservation, and restoration of cultural heritage.
Author: Antonio Doménech-Carbó, Universitat de València (Spain), http://www.uv.es/uvweb/analytical-chemistry-department/en/administrative-technical-staff/organisation-chart-1285859984083.html
Title: Dating Archaeological Copper/Bronze Artifacts by Using the Voltammetry of Microparticles
Angewandte Chemie International Edition, Permalink to the article: http://dx.doi.org/10.1002/anie.201404522
Antonio Doménech-Carbó | Angewandte Chemie
Pathogenic bacteria hitchhiking to North and Baltic Seas?
22.07.2016 | Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung
Unconventional quasiparticles predicted in conventional crystals
22.07.2016 | Max-Planck-Institut für Chemische Physik fester Stoffe
Munich Physicists have developed a novel electron microscope that can visualize electromagnetic fields oscillating at frequencies of billions of cycles per second.
Temporally varying electromagnetic fields are the driving force behind the whole of electronics. Their polarities can change at mind-bogglingly fast rates, and...
Breakup of continents with two speed: Continents initially stretch very slowly along the future splitting zone, but then move apart very quickly before the onset of rupture. The final speed can be up to 20 times faster than in the first, slow extension phase.phases
Present-day continents were shaped hundreds of millions of years ago as the supercontinent Pangaea broke apart. Derived from Pangaea’s main fragments Gondwana...
Scaffolding and specialised workers help with the delivery – Heidelberg biochemists gain new insights into biogenesis
A type of scaffolding on which specialised workers ply their trade helps in the manufacturing process of the two subunits from which the ribosome – the protein...
Scientists at the Helmholtz Zentrum München have developed a new mass spectrometry imaging method which, for the first time, makes it possible to analyze hundreds of metabolites in fixed tissue samples. Their findings, published in the journal Nature Protocols, explain the new access to metabolic information, which will offer previously unexploited potential for tissue-based research and molecular diagnostics.
In biomedical research, working with tissue samples is indispensable because it permits insights into the biological reality of patients, for example, in...
Chemists at the University of Basel have succeeded in using computer simulations to elucidate transient structures in proteins. In the journal Angewandte Chemie, the researchers set out how computer simulations of details at the atomic level can be used to understand proteins’ modes of action.
Using computational chemistry, it is possible to characterize the motion of individual atoms of a molecule. Today, the latest simulation techniques allow...
15.07.2016 | Event News
15.07.2016 | Event News
11.07.2016 | Event News
22.07.2016 | Information Technology
22.07.2016 | Physics and Astronomy
22.07.2016 | Life Sciences